Most shore birds gather in summer around the large harbours and estuaries of northern New Zealand. Mudflats and soft sands are exposed at low tide and provide rich feeding grounds for long-legged wading birds such as godwits, oystercatchers, stilts and herons. A few are year-round residents, but many are migratory visitors – from the Arctic or up from the South Island.
There is little bird life on exposed surf and gravel beaches, apart from the ubiquitous gulls, ever on the scrounge. Rocky coasts are also poor bird-spotting areas, although red-billed gulls will nest on rocky headlands and gannets colonise the clifftops.
Breeding on the coast
Shore birds breed in spring or early summer and nest on the ground above the high-tide mark. For many wading birds and terns, a nest is simply a shallow scrape in the ground. Gulls arrange sticks, grass and seaweed into a substantial construction. Shore-bird eggs and hatchlings are well camouflaged – brown, grey or sandy yellow, splotched with darker markings.
Before humans and their camp-follower mammals arrived on New Zealand shores, coastal birds faced relatively few threats. Unseasonal storm waves could sweep away nests, sands could bury eggs and chicks, predatory black-backed gulls might consume nestlings, but overall, shore birds thrived.
Since the late 19th century some shore-bird populations have seriously declined. By 2004:
- shore plovers had disappeared from mainland New Zealand and were found naturally only on the Chatham Islands.
- New Zealand fairy terns were reduced to 36, and bred only at three sites in Northland.
- New Zealand dotterels were down to 1,500 birds; 200 or so formed a Stewart Island population, the rest were confined to northern coasts.
Stoats, rats, cats and hedgehogs are a major threat to nesting shore birds because they sniff out defenceless chicks and eat eggs. Until 1940 it was legal to shoot shore birds; Europeans took thousands for sport and food. In summer hordes of holidaymakers descend on the coast, frightening adult birds off their nests. Off-road vehicles hurtle along the high-tide line, crushing camouflaged eggs and flightless chicks. Since the 1970s the coast has become prime real estate, and breeding habitats near beachfront subdivisions have all but disappeared.